A common sealed organic EL device is illustrated in FIG. 17, in which a laminate of a transparent anode 2, an organic EL layer 3 and a cathode 4 in this order is formed on the surface of a transparent substrate 1, and a close-topped cylindrical sealing member 6 is fixed on the substrate 1 through an adhesive (a) such that it covers the laminate. The adhesive is applied to an open mouth surface of the sealing member 6. The sealed organic EL device is manufactured by sealing the laminate of the transparent anode, the organic EL layer and the cathode in between the transparent substrate 1 and the sealing member 6 through the adhesive.
However, the organic EL devices have a short life and drastically reduce emitting performances such as emission brightness and emission homogeneity from the initial levels after a duration of time. These deteriorations in emitting performances are known to be attributed to moisture formed inside the sealing member 6 or moisture that has penetrated through the adhesive (a) into the organic EL device, deteriorating the organic EL device inside the sealing member 6. To avoid this problem, a moisture absorbent (b) is provided in, for example, between the organic EL device and the sealing member 6.
Patent Literature 1 addresses the prevention of organic EL devices from deterioration by moisture formed inside a sealing member 6 or moisture that has penetrated through an adhesive (a) inside the sealing member 6. In detail, it discloses a process for sealing an organic EL device with a transparent substrate 1 and a sealing member 6, wherein the sealing is preceded by atmospheric pressure plasma treatment of mating surfaces of the transparent substrate 1 and the sealing member 6 which will be in contact together by the sealing. According to this process, the treatment for the transparent substrate 1 removes a layer (c) such as SiO2 layer on the surface of the substrate 1 and roughens the treated surface by means of atmospheric pressure plasma, and the treatment for the sealing member activates and roughens the treated surface with atmospheric pressure plasma. The patent literature describes that the treated surfaces can be joined together closely and thereby the life of the organic EL devices is extended.
As described hereinabove, an organic EL device is generally sealed in such a manner that a substrate 1 and a sealing member 6 are bonded together via an adhesive (a) which has been provided in an area free of the organic EL device on the substrate 1. Accordingly, the organic EL device is not usually formed in the vicinity of the outer periphery of the substrate 1.
When an organic EL layer 3 is formed by depositing a low-molecular weight compound, the use of a deposition mask facilitates the selective formation of an organic emitting layer in a central area of a substrate 1 inside the outer periphery of the substrate 1. However, when an organic EL layer 3 is formed by applying (for example, spin coating) a high-molecular weight compound, difficulties are encountered in forming an organic emitting layer selectively in a central area of a substrate 1 while avoiding the outer periphery of the substrate 1. If an organic EL layer 3 is formed on an outer peripheral area of a substrate 1, the organic EL layer 3 found on the outer peripheral area of the substrate 1 should be removed to expose the substrate 1 in preparation for the application of an adhesive (a).
Patent Literature 2 discloses a process for producing organic EL display devices having an emitting part (an organic EL device) and a non-emitting part on a substrate. In detail, a liquid repellent part is formed between an emitting part and a non-emitting part, thereafter at least one of organic layer(s) is formed by an application method, and the organic layer formed on the non-emitting part outside the liquid repellent part is wiped away with a solvent. According to this process, an organic emitting layer formed on an outer peripheral area of a substrate 1 may be removed.
The atmospheric pressure plasma surface treatments include direct methods in which gas discharge is generated directly between an electrode and a treatment subject, and indirect methods in which excited active species are formed by discharge between a power electrode and a grounding electrode and a gas stream containing the active species is injected to the surface of a treatment subject. The indirect methods have a lower treatment rate than the direct methods and may therefore require high power. Meanwhile, the indirect methods are free from concerns about damages to the treatment subject due to the charging up or the arc discharge, and allow for local surface treatment coping with the configuration of treatment subject or limited range of treatment, by changing the shape of a nozzle injecting the gas stream or by controlling the flow rate of the gas. Such indirect plasma surface treatment methods and apparatuses used therein are disclosed in, for example, Patent Literatures 3 and 4.
Techniques to remove organic substances by plasma irradiation include plasma ashing in which an organic photoresist that has remained on a substrate after dry etching in photolithography is removed by being decomposed by plasma in a gas phase (for example, Patent Literatures 5 and 6).